The present invention is particularly applicable, but not necessarily restricted to the manufacture of resilient perforated contoured panels of the type employed for trimming the interior of passenger compartments of automobiles and the like. More particularly, the process provides for distinct benefits and advantages in the manufacture of resilient headliners of the so-called snap-in type which are adapted to be positioned adjacent to the underside of steel roof panels of vehicles in order to impart the desired aesthetic appearance and to further provide insulation against the transmission of noises into the interior of the passenger compartment.
A variety of materials and structures have heretofore been used or proposed for use in the fabrication of snap-in type headliners of which those disclosed in U.S. Pat. Nos. 3,506,532 and 3,507,728 are typical. Considerations of costs, ease of installation, weight, durability and sound and heat insulation have occasioned the use of composite laminar sheets comprised of a foam core incorporating one or two impervious face sheets bonded to the surfaces of the core as a material for use in the manufacture of such headliner panels. Composite foam core structures of the foregoing type comprised of thermoplastic polymers are particularly suitable because of their ability to be thermoformed to a variety of contours including recesses or embossments for accommodating accessory equipment such as windshield visors, safety belt harnesses, radio speaker housings or the like.
A continuing problem associated with the manufacture of composite contoured trim panels comprised of thermoplastic foam core laminates has been the formation of undesirable surface irregularities in the localized areas surrounding perforations or apertures through the panel which in many instances are visible in spite of the use of decorative coatings or layers detracting from the aesthetic appearance of the trim panel. The provision of such perforations over all or over selected portions of the panel are desirable in some instances to provide for controlled modifications in the acoustical characteristics of the panel. In order to overcome such a dimpling or surface distortion of perforated panels it has heretofore been proposed to first thermoform the panel in an imperforate condition to a desired molded contour and thereafter impart perforations to the resultant contoured panel. This proposal has been found commercially unsatisfactory because of the high cost of tooling required to effect satisfactory perforation of a contoured panel due to the fragile nature of the composite foam core sheet.
The process of the present invention overcomes many of the problems and disadvantages associated with prior art techniques by providing a simple, economical and efficient method whereby perforated thermoplastic composite foam core laminates can be thermoformed to produce a resultant panel in which the faces thereof are substantially devoid of any surface irregularities or dimples in the vicinity adjacent to the perforations thereby providing increased versatility in the types of decorative finishes that can be applied and further enhancing the appearance of the resultant contoured trim panel.